The Doctor and Rory assemble an army to free Amy and her child, unaware that they've been led into a trap.

Months ago, Amy Pond (Karen Gillan), Rory Williams (Arthur Darvill) and River Song (Alex Kingston) were stunned to see the Doctor (Matt Smith) murdered by someone in an old NASA spacesuit. Traveling to the past with a younger version of The Doctor (who was unaware of his future fate), they encountered a young girl trapped in the spacesuit. Amy also began having visions of a woman with an Eye Patch even before she was captured by the Silence and confronted with evidence that the young girl was her daughter. Although Amy was soon freed, the young girl slipped away and later regenerated as a Time Lord would.

While Amy and Rory conspired to keep the Doctor's fate a secret from him, he kept a secret from them as well. After a mission that unveiled the origins of "The Flesh," the Doctor revealed that Amy had been taken months ago and replaced by a "Flesh" duplicate piloted by Amy's own consciousness. The Doctor promised to find her before severing the connection and dissolving the fake Amy. Somewhere else, Amy awoke and found herself nine months pregnant. The mysterious woman with the Eye Patch then stated that Amy was about to give birth.

Story:

Some time later, the Eye Patch Lady, aka Madame Kovarian (Frances Barber) and a group of armed soldiers watch over Amy as she gets a few moments with her daughter, Melody Pond. She tells Melody about her father, a legendary figure known as "The Last Centurion." At a Cybermen base, Rory emerges in a Centurion costume and demands to know where his wife is. He also brings a message from the Doctor in the form of the destruction of the rest of the Cyber fleet. Once Rory and the Doctor learn that Amy is being held at the asteroid base known as Demon's Run, they start recruiting the Doctor's allies to help them save Amy.

The Doctor successfully brings in a Sontaran Commander/Nurse Strax (Dan Starkey), a 19th Century Silurian known as Madame Vastra (Neve McIntosh) and her human lover, Jenny (Catrin Stewart) as well as a black market trader named Dorium Maldovar (Simon Fisher-Becker). However, Rory is stunned when River Song refuses the Doctor's request for help and says that she can only come at the end. On the asteroid base, Amy has an unlikely ally in the form of Lorna Bucket (Christina Chong), a young woman who once met the Doctor as a child. Lorna gives Amy a token with Melody's name written on it in the language of her people. In return, Amy warns Lorna to be on the Doctor's side when he arrives, for her own good.

Aboard the base, Colonel Manton (Danny Sapani) explains to his fanatical soldiers that they have sided with the Headless Monks to kill the Doctor. But the Doctor reveals himself to be in disguise as one of the Monks and he tricks the two sides into attacking each other. The Doctor's friends then stage an assault on the base and take it without killing anyone themselves; which Vastra describes as the Doctor's greatest achievement. Amy is joyously reunited with her daughter and husband, as well as the Doctor. However, Lorna overheard Kovarian state that the entire operation was an elaborate trap for the Doctor.

After driving off Kovarian and her forces, the Doctor, Vastra and Dorium learn that Melody Pond may be part Time Lord. And to his horror, the Doctor realizes that it may have happened because Rory and Amy consummated their marriage on the TARDIS. Lorena then reappears and warns the team that the Headless Monks are still on the station, moments before they attack and kill Dorium. Back in the lab, Kovarian contacts the Doctor and gloats that Melody will be a weapon to be used against him. She also states that she has now fooled the Doctor twice in the same way.

In the battle against the Headless Monks, Lorena and Strax are fatally wounded. Amy's baby is also revealed to be a Ganger, which dissolves in her arms. Distraught, Amy recoils from the Doctor's touch. Then River Song appears, leading the Doctor to berate her for not answering his call for help. She tells him that she couldn't have prevented this and lays the blame squarely at his feet for allowing himself to become so feared that his enemies have become desperate for a weapon to use against him like Melody. Incensed, the Doctor finally demands that River tell him who she really is. But she insists that she is telling him.

Finally realizing who he's speaking with, the Doctor becomes almost giddy. He then retreats back to the TARDIS and vows to Amy and Rory that he will find their child before leaving them in River's care. Angered and confused, Amy threatens River with a gun to learn what she told the Doctor. River gives Amy the charm that Lorena had given her earlier. And before Amy's eyes (and as River explains) the alien letters form River's name as the closest approximation Lorena had for Melody's name in the language of Lorena's people. To reiterate, River tells Amy and Rory that she is their daughter, Melody.

Breakdown:

It's a testimony to Steven Moffat's writing skills that I still really enjoyed watching this episode multiple times even though I had guessed about River's connection to Amy and Rory earlier this season; after we learned that Amy's daughter had Time Lord traits. If Moffat had any missteps in laying that out, the only glaring error that I can see is that he didn't leave any other real possibilities for River's identity.

I know I harp on Moffat quite a bit, but he really is a great "Doctor Who" writer. It amazes me that he still has some detractors, because his stories are some of the best "Who" since the relaunch in 2005. "A Good Man Goes To War" was an epic from start to finish, especially during the opening moments in which Rory delivered the Doctor's message to the Cybermen. The cliffhanger is also intriguing in that it's hard to see Amy and Rory going back to the TARDIS as the Doctor's companions after this. We also know that the Doctor didn't recover Melody before the Silence put her the spacesuit as a little girl in the 1960s. And we still don't know how this ties in with the Silence or the Doctor's impending death.

Before we move on, I do want to point out that I'm not sure if Moffat has entirely played fair about River's true identity. I think that he did know she was part Time Lord in her first appearance, since he went out of his way to suggest that no Time Lord could survive what ultimately killed River. But River was pretty nonchalant around Amy last season and she didn't seem to know who Rory was in the fifth season finale. For that matter, how could River have stayed in the timeline when Rory was erased from history? That would take some explaining if Moffat or the other writers ever decide to address it.

We've seen Kovarian in nearly every episode this season, but this was our first real look at the Doctor's latest adversary. Frances Barber was pretty convincing as the leader of an anti-Doctor coalition who seems to have personal grudge against him. (Maybe he's responsible somehow for the loss of her eye?) The compelling part of her character is that she seems to believe that her crusade against the Doctor is righteous. She's clearly the villain of the piece, but I doubt she sees it that way.

It was an interesting choice to make most of the Doctor's allies characters that we've never met before. Commander Strax was a lot of fun, particularly when he insisted that he was the perfect choice to breastfeed Melody. Vastra and Jenny felt like they stepped out of some "Doctor Who" spinoff that we've never seen. The only thing about those two that seemed off was the 19th century setting. I just didn't believe in that. Lorena was actually the character that made the strongest impression, so much so that I assumed that she was being groomed as the Doctor's next companion… if Amy and Rory depart this season. Her death and Strax's actually had some emotional punch.

All three leads had a field day in this episode. Matt Smith has found his inner angry Doctor, which rivals David Tennant's Tenth Doctor for his intensity. I also liked his sudden reversion to an almost giddy state upon realizing River's identity. That was very him. Karen Gillian had a lot of strong material too as a fiercer Amy Pond than we've seen before. But it was Arthur Darvill who stood out with a dynamite performance as Rory; who has really become a hero in his own right this season. Rory's a long way from the bumbling character he was at the beginning of season five.

My main complaint about this episode is that we'll have to wait several months to see how it all plays out. I was never in favor of this mid-season break and I hope that it won't become a common "Doctor Who" schedule in the future. I'm usually patient between seasons, but this is going to make the summer a lot longer.

At least we have "Torchwood" coming up in a few weeks. By the time that's over, the rest of "Doctor Who" season six should be right around the corner.